Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 180-186).

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 147-153).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (197-203).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1972. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 185-190).

The discovery, isolation, and ultrastructural investigation of a lytic virus infection in the naked, marine phytoflagellate, Micromonas pusilla, are described. Infected cells were first seen in April, 1975, during a transmission electron microscope examination of a week old enrichment culture containing nanoplankton collected at the mouth of the Burrard Inlet in Vancouver, British Columbia. Selective lysis occurred in this culture» removing nearly all M. pusilla cells without visibly affecting the other microflagellate populations. Ultrastructural examination of the culture indicated the presence of polyhedral inclusions within cells of M. pusilla. Medium from this infected culture was observed to cause the destruction of unialgal strains of M. pusilla maintained in the Northeast Pacific Culture Collection. Ultrastructural studies of the host organism, M. pusi11a, confirmed the earlier findings of Manton and Parke (1959) and provided additional information on the fine structure of this nanoflagellate. Terminal flagellar hairs, a vestigial, second basal body, and a peripheral system of microtubules are described. The polyhedral virus particles in situ within infected cells, or when isolated and negatively stained with uranyl acetate, appear tail-less and present profiles consistent with their having icosahedral symmetry. The virions have an average diameter of 135 nm. Surface substructures analogous to viral capsomeres were observed on partially disrupted particles. Viral entry takes place within 15 minutes following introduction of inoculum and occurs by localized fusion of adjacent cell and virus surfaces, followed by direct penetration of viral genome. After an eclipse period of approximately three hours in duration progeny virus appear in the perinuclear cytoplasm. Associated with the viral assembly process are cytoplasmic fibrils and clusters of membrane-bound vesicles. Viral egress occurs by localized rupture of the plasmalemma. Viral activity is monitored by an assay system based upon the reduction in the in vivo chlorophyl1 a fluorescence of infected cells. Solutions of virus particles stored at 4°C in millipore-filtered, autoclaved seawater or culture medium retain their infective capacity for nine months. The virus is stable in a pH range between 4 and 10. Thermal inactivation occurs between 55° and 63°C. Host range studies indicate that the lytic properties of the virus are probably specific to M. pusilla. The virus has been designated Micrbmbnas pusilla virus, MPV. / Science, Faculty of / Botany, Department of / Graduate

Bibliography: pages 76-89. / This study examines the effects of enrichment with organic carbon and nitrogen on inorganic nitrogen partitioning between phyto- and bacterio- plankton. Strongly preferential uptake of ammonium over nitrate was observed by both the phytoplanktonic and bacterial fractions, with RPINH4 values typically between 1 and 5. The bacterial fraction ( <0.8μm) was found to be responsible for as much as 48-75% of community uptake of ammonium; while the netplanktonic fraction was observed to take up approximately 50% of intact community uptake of nitrate. The addition of amino acids appeared to mediate bacterial competition for ammonium, indicating their preference for DON as a nitrogen source and allowing increased ammonium uptake by the nanoplanktonic fraction. The effect of glucose enrichment was complicated by the presence of protozoans, which appeared to be indirectly responsible for decreased ammonium uptake due to depletion of this substrate in the presence of added glucose. The nanoplankton appeared to be responsible for the least nitrogen uptake with respect to biomass, indicating that they may have been subject to competition pressure from both the bacterial and netplanktonic fractions.

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Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 249-272).

Thesis (M.Sc.)--College of William and Mary. / Vita. Includes bibliographical references. Also available online.

Thesis (Ph.D.)--University of Rhode Island, 2009. / Includes bibliographical references (leaves 122-138).